1. Field of the Invention
This invention relates to security devices and more particularly to a mechanical door latch.
2. Prior Art
Door securing devices commonly in use include locks, slide bolts, slide chains, and the like. Although locks, particularly of the bolt action type, provide a measure of security, they are ineffective in any public use areas such as hotels and motels where the establishment must have a master key. The mere existance of a master key, or duplicate keys, creates the possibility of a copy of the copy falling inappropriate hands.
Slide bolts, as presently used, do not provide a significant measure of protection, first, because they are generally relatively flimsy, second, because they are screwed into the door which does not provide a firm base and third, because over the years they will become misaligned and become difficult or impossible to activate. Further, their use is not favored in public use buildings such as hotels and motels because they may be difficult to operate thereby providing a fire hazard and because such establishments must allow for the possibility of emergency entry into the locked room from the outside without major damage. Chain locks provide more of a psychological than a physical deterent. Anybody having access to a master or duplicate key will find a chain lock to present no barrier since, even if it cannot be worked from the exterior with the door partially opened, it can easily and quietly be cut.
In view of the above restrictions with known devices it has been suggested, in the past, to use other forms of hinged or swinging latch devices having a portion affixed to the door frame and a swing or slide portion extendable into an overlapping relationship with the door. These devices have generally required engagement with a door carried member thereby relying in part upon the strength of the anchor to the door while further having the same misalignment problems discussed above in connection with slide bolts. Additionally provision has not been made in such prior devices for intentional disassembly from the outside when necessary.
It would therefore be an advance in the art to provide an improved security latch which is not dependent upon the strength of any mounting portion attached to the door, which is easily and quickly actutable, which does not require alignment of co-fitting parts and which, if necessary, can be deactivated from exterior of the locked room by methods which are not easily surreptitiously carried out.